Since the removable disk is identified as the cheap element, why not backup to one locally and periodically copy the backup to a second one, which you store offsite.
As for cloud storage, are you planning to rely on cloud for your “building burns down” backup, but trying to save on volume? In that case, I agree with @drwtsn32 - the risk is not worth the savings. See this thread about Inexpensive Cloud Storage Options. Put your whole backup there, intact.